AD9920ABBCZ datasheet(47/112 Pages) AD

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AD9920A

Rev. B | Page 47 of 112

Multiplier Mode

To generate very wide vertical timing pulses, a vertical region

can be configured into a multiplier region. This mode uses the

V-pattern registers in a slightly different manner. Multiplier

mode can be used to support unusual CCD timing requirements,

such as vertical pulses that are wider than the 13-bit V-pattern

toggle position counter. In general, the 13-bit toggle position

counter can be used with the sweep mode feature to support

very wide pulses; however, multiplier mode can be used to

generate even wider pulses.

The start polarity and toggle positions are still used in the same

manner as in the standard V-pattern group programming, but

VLEN is used differently. Instead of using the pixel counter

(HD counter) to specify the toggle position locations (VTOG1,

VTOG2, VTOG3, and VTOG4) of the V-pattern group, the

VLEN is multiplied by the VTOG position to allow very long

pulses to be generated.

To calculate the exact toggle position, which is counted in pixels

after the start position, use the following equation:

Multiplier Mode Toggle Position = VTOG × VLEN

Because the VTOG register is multiplied by VLEN, the resolu-

tion of the toggle position placement is reduced. If VLEN = 4,

the toggle position precision is reduced to four-pixel increments

instead of to single-pixel increments. Table 20 summarizes how

the V-pattern group registers are used in multiplier mode opera-

tion. In multiplier mode, the VREP registers must always be

programmed to the same value as the highest toggle position.

Figure 59 illustrates this operation. The first toggle position is 2,

and the second toggle position is 9. In nonmultiplier mode, this

causes the V-sequence to toggle at Pixel 2 and then at Pixel 9

within a single HD line. However, in multiplier mode, toggle

positions are multiplied by the value of VLEN (in this case, 4);

therefore, the first toggle occurs at Pixel 8, and the second toggle

occurs at Pixel 36. Sweep mode is also enabled to allow the

toggle positions to cross the HD line boundaries.

Table 20. Multiplier Mode Register Parameters

Length (Bits)

Range

Description

MULT_SWEEPx

High/low

High enables multiplier mode.

VPOL

High/low

Starting polarity of XV1 to XV24 signals in each V-pattern group.

VTOG

0 to 8191 pixel

location

Toggle positions for XV1 to XV24 signals in each V-pattern group.

VLEN

0 to 8191 pixels

Used as multiplier factor for toggle position counter.

VREP

0 to 8191 pixel

location

With VREP_MODE = 0, VREP_EVEN must be set to the same value as the highest VTOG

value. VREP_ODD and VREPA can be set to 0.

XV1 TO XV24

VLEN

341

2341

234

1234

123

4123

412

3412

341

2341

234

START POSITION OF VPAT GROUP IS STILL PROGRAMMED IN THE V-SEQUENCE REGISTERS

PIXEL

NUMBER

345

6789 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

MULTIPLIER MODE V-PATTERN GROUP PROPERTIES:

1START POLARITY (STARTPOL = 0).

2FIRST, SECOND, AND THIRD TOGGLE POSITIONS (VTOG1 = 2, VTOG2 = 9).

3LENGTH OF VPAT COUNTER (VLEN = 4); THIS IS THE MINIMUM RESOLUTION FOR TOGGLE POSITION CHANGES.

4TOGGLE POSITIONS OCCUR AT LOCATION EQUAL TO (VTOG × VLEN).

5IF SWEEP REGION IS ENABLED, THE V-PULSES MAY ALSO CROSS THE HD BOUNDARIES, AS SHOWN ABOVE.

Figure 59. Example of Multiplier Region for Wide Vertical Pulse Timing

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